Automatic analyzer

ABSTRACT

An automatic analyzer which combines a measured volume of a liquid sample with measured volumes of reagents in proper order, mixes and times the reacting liquids, and senses resulting liquid color by pouring the mixture through a colorimeter. The analyzer has only one major moving part - a driven center tube mounting measuring and feeding units, mixing units, and mixing and holding units, with the tube serving as a conduit between units and to the colorimeter. A measuring and feeding unit, upon rotation of the tube, dips a lifting passage into an underlying supply of fluid, lifts a quantity of the fluid by rotation of the passage, pours the liquid into an adjustable measuring pocket with the excess spilling back into the container, and finally pours the measured volume into the tube. The mixing unit receives liquid and spills it through a tortuous path upon rotation before returning the then mixed liquid to the tube. The mixing and holding unit spills liquid along a spiraling passage before returning it to the tube and thus holds the liquid for the number of tube revolutions equaling the coils in the spiral of the passage. The tube itself is slightly inclined so that liquid flows under gravity from unit to unit eventually to the colorimeter.

United States Patent 11 1 Hach AUTOMATIC ANALYZER [75] Inventor:Clifford C. l-Iach, Ames, Iowa [73] Assignee: IIach Chemical Company,Ames,

Iowa

- 221 Filed: Aug .22, 1972 21 Appl. No.: 282,729

[52] US. Cl. 356/181, 23/253 R, 23/259, 73/244, 250/218, 259/89, 356/36,356/196 [51] Int. Cl. G0lj 3/46, GOln 1/00, G02f 3/04 [58] Field ofSearch 356/36, 180, 181, 356/182, 246, 196, 197; 250/218; 259/89;

[56] References Cited UNITED STATES PATENTS 3,712,144 l/l973 Kuzel et a1356/36 3,364,865 l/1968 Theuriaux 73/244 Primary Examiner-DavidSchonberg Assistant Examiner-V. P. McGraw Attorney-C. Frederick Leydiget al.

[57] ABSTRACT An automatic analyzer which combines a measured NOV. 20,1973 volume of a liquid sample with measured volumes of reagents inproper order, mixes and times the reacting liquids, and senses resultingliquid color by pouring the mixture through a colorimeter. The analyzerhas only one major moving part a driven center tube mounting measuringand feeding units, mixing units, and mixing and holding units, with thetube serving as a conduit between units and to the colorimeter. Ameasuring and feeding unit, upon rotation of the tube, dips a liftingpassage into an underlying supply of fluid, lifts a quantity of thefluid by rotation of the passage, pours the liquid into an adjustablemeasuring pocket with the excess spilling back into the container, andfinally pours the measured volume into the tube. The mixing unitreceives liquid and spills it through a tortuous path upon rotationbefore retuming the then mixed liquid to the tube. The mixing andholding unit spills liquid along a spiraling passage before returning itto the tube and thus holds the liquid for the number of tube revolutionsequaling the coils in the spiral of the passage. The tube itself isslightly inclined so that liquid flows under gravity from unit to uniteventually to the colorimeter.

11 Claims, 14 Drawing Figures AUTOMATIC ANALYZER This invention relatesgenerally to automatic chemical analyzers and more particularly concernsa continuous analyzer for colorimetrically monitoring a givencharacteristic of a flowing liquid sample over long periods of time.

Chemical analyzers which react to a color change in the sample underinvestigation upon the addition of one or more reagents normally dependfor accuracy upon bringing together closely controlled amounts ofreagent and sample. Such accurate metering has, in the past, beenachieved with precision pumps or with capillary passages. However, pumpsfor this purpose are usually intricate and expensive, and capillarymetering is subject to clogging problems and is dependent upon viscositywhich, in turn, is a function of temperature which must therefore becontrolled. Despite such problems, however, continuous automatictesting, particularly of water intended for any one of a variety ofuses, has become an increasingly sought-after objective. Continuousmonitoring of a flowing water supply for acidity, chlorine or fluoridecontent, hardness, and/or iron or other metallic concentrations, to namejust a few characteristics, is of value in water treatment plants, powerstations and other industrial and agricultural situations.

The general aim of the invention is to provide an improved analyzer thatis economical to manufacture and operate, requiring virtually nomaintenance, and which functions accurately and reliably withoutviscosity, i.e. temperature, control.

It is also an object of this invention to provide an analyzer ascharacterized above which is rugged and damage-resistant in thatmeasuring, mixing, and aging or timing functions are carried out by asolid, single assembly, so that even relatively complex tests areautomatically and repeatedly run with what is virtually a single movingpart.

Another object is to provide an analyzer of the above described typewhich is made up of components that can be assembled in groups,arrangements and proportions to perform a wide variety of tests varyingin number and quantity of reagents employed, and in timing or aging ofthe reaction steps.

A further object is to provide an analyzer as referred to above which,for accuracy and reliability, mechanically measures and mixes, andmechanically times or ages under the control of an ordinary synchronousmotor.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in

y rhich:

FIG. 4 is a fragmentary section taken approximately along the line 4-4in FIG. 3;

FIG. 5 is a fragmentary section corresponding to FIG. 4 but showing theunit in an alternate operating position;

FIG. 6 is a section taken approximately along the line 6-6 in FIG. 4;

FIG. 7 is an enlarged fragmentary longitudinal section of another one ofthe units shown in FIG. 1;

FIG. 8 is a section taken approximately along the line 88 in FIG. 7;

FIG. 9 is a fragmentary section taken approximately along the line 99 inFIG. 8; and

FIG. 10 is an enlarged fragmentary section taken along the line l010 inFIG. 1.

While the invention will be described in connection with a preferredembodiment, it will be understood that I do not intend to limit theinvention to that embodiment. On the contrary, I intend to cover allalternatives, modifications and equivalents as may be included withinthe spirit and scope of the invention as defined by the appended claims.

Turning to the drawing, there is shown an analyzer 10 embodying theinvention and including a number of sub-components arranged to testwater introduced through a line 11 at a rate determined by the settingof a valve 12. To illustrate the construction and operation of theinvention, the analyzer 10 is set up to test for silica in the watersample using the heteropoly blue method in which a water sample istaken; ammonium molybdate in an amount equaling a 50th part of the watervolume is added, mixed and held for 5 minutes; oxalic acid in an amountequaling a 50th part of the water sample volume is next added and mixed;and finally an amino acid solution in an amount equaling a 50th part ofthe water sample volume is added, mixed and held for another 5 minutes.A blue color developed in the solution is indicative of the presence ofsilica in the water sample. The analyzer 10 performs this testautomatically and repeatedly on water flowing in from the line 11. Itwill be apparent, once the analyzer is understood, that otherarrangements of the analyzer components can be assembled to perform awide variety of other test procedures involving measuring, mixing,holding and color checking of thesample and test reagents.

The components of the analyzer 10 include a center tube 15 rotatablydriven by a synchronous motor 16, a sample measuring and feeding unit17, a pair of reagent measuring, mixing and holding units 18 and 19, areagent measuring and mixing unit 20, and a colorimeter 21 of theflow-through type. The units 17-20 are all fixed on the tube 15 forsimultaneous rotation with the tube, and the reagent units 18-20 areenclosed in tanks 22, 23 and 24 containing, respectivelyfammoniummolybdate, oxalic acid and a solution of amino acid. The sample unit 17also rotates on the tube 15 into a container 25 which receives water fortesting from the line 11 through the valve 12. All of the components ofthe analyzer 10 are supported in a suitable frame 26, schematicallyindicated, which includes a discharge line 27 for draining the water andreagent solution from the analyzer following testing.

Considering first the measuring and feeding of the water sample, theunit 17 includes a body 30 having a liquid receiving core fitted tightlyaround the tube 15 which defines the axis about which the body 30rotates.

The body 30 defines a measuring pocket 31 adjacent the core and havingan open top leading to an opening 32 in the tube 15. The pocket 31 alsohas a spill wall side whose edge 33 defines the top of the pocket 31 andthus the upper level of liquid in the pocket when the pocket is disposedbeneath the axis of the tube 15 (see FIG. 2a).

The body 30 also includes a cup and tube defining a lifting passage 34leading from the top of the pocket 31 to a point well spaced from theaxis of the tube 15, with the passage 34 having a bottom surfacegenerally facing the axis of the tube so that rotation of the body onthe tube with the tube axis generally parallel to the water in thecontainer 25 will sequentially cause the bottom of the passage 34 to dipinto the liquid, raise a quantity of liquid from the supply and pour theraised liquid quantity into the pocket 31 the sequence illustrated inFIGS. 2 and 2a. The passage 34, particularly the cup portion thereof, isproportioned to raise and pour into the pocket 31 a volume of liquidsignificantly greater than that retained by the pocket spill wall side.Preferably, the passage 34 is also sufficiently large in diameter thatthe liquid flows smoothly without bridging across the passage. The edge33 of the spill wall is rounded and made hydrophilic so that liquidspills smoothly thereover with a minimum capillary effect from surfacetension, and the edge 33 is also curved about the axis of the tube 15 soas to maintain a substantially fixed wall height through a range ofrotation of the body 30 about that axis. In the illustrated embodiment,the hydrophilic property is imparted to the spill wall edge 33 byforming the body of polyvinyl chloride and slightly roughening thatedge, as by sanding or chemical etchmg.

As a result of the spill wall configuration, a precise volume of liquidis retained in the pocket 31, the excess spilling over the spill walledge 33, with the top of the retained liquid being almost exactly at thespill wall edge when the pocket is beneath the tube 15 (see FIG. 211).To adjust this precisely measured volume, a member 35 is adjustablymounted, in this case by a threaded connection, for movement into andout of the pocket 31 so as to permit selective variation of the pocketvolume. Once having been measured, the liquid content of the pocket 31is poured into the tube 15 through the opening 32 upon continuingrotation of the tube (see FIG. 2b). In keeping with the analysisperformed by the analyzer 10, the unit 17 measures and feeds into thetube ml. of water sample upon each tube revolution.

The measuring portions of the units 18-20 are structurally virtuallyalike and conceptually similar to the structure and operation of theunit 17. Taking the unit 18 as representative, it includes a body 40 inthe form of a disk having a liquid receiving core tightly fitted on thetube which defines the axis about which the body 40 rotates (see alsoFIG. 3). The body 40 defines a measuring pocket 41 adjacent the core andhaving an open top leading to an opening 42 in the tube 15 (see alsoFIG. 4). The pocket 41 also has a spill wall side whose edge 43 definesthe top of the pocket and thus the upper level of liquid in the pocketwhen the pocket is beneath the axis of the tube 15 (see FIG. 3a).

The body 40 is formed with a spiral groove in its outer face defining alifting passage 44 leading from the top of the pocket 41 to a point wellspaced from the axis of the tube 15, with the passage 44 having a bottomsurface generally facing the tube axis so that rotation of the body onthe tube with the tube axis generally par- I side 43. Preferably, thegroove forming the passage is sufficiently large that the liquid flowssmoothly without bridging across. The edge 43 of the spill wall isrounded and made hydrophilic so that liquid spills smoothly thereoverwith a rninumum capillary effect, and the edge 43 is also curved aboutthe axis of the tube 15 to maintain a substantially fixed wall heightthrough a range of body rotation about that axis. As was the case in theunit 17, the hydrophilic property can preferably be imparted to thespill wall edge 43 by forming the body 40 of PVC and slightly rougheningthe edge 43 as by sanding or chemical etching.

As a result of the spill wall configuration, a precise volume of liquidis retained in the pocket 41 upon rotation of the tube 15, the excessfalling over the spill wall with the top of the liquid retained beingalmost exactly at the spill edge 43 when the pocket is beneath the tube15 (see FIG. 3a). To adjust this measured volume, a member 45 isadjustably mounted, in this case by a threaded connection 46, in thebody 40 for movement into or out of the pocket 41 so as to permitselective variation of the pocket volume. Once measured, the fluidreagent in the pocket 41 is poured into the tube 15 through the opening42 upon continuing rotation of the tube. Again, following through withthe analysis performed by the analyzer 10, the unit 18 measures andfeeds into the tube 0.1 ml. of ammonium molybdate upon each tuberevolution.

The center tube 15 is slightly inclined (see FIG. 1) so that there isgravity flow of liquid from the high end, on which the sample unit 17 isfixed, to the low end, under which the colorimeter 21 is mounted. Theends of the tube are sealed by plugs 47 and 48, the plug 48 carrying apin 49 rotatably seated in the frame 26 so as to define a bearing andthe plug 47 being formed to slide over an irregularly shaped outputshaft 51 forming part of the motor 16. The tube 15 is thus drivinglyconnected to the motor, although it can be easily removed from theanalyzer frame for cleaning or other servicing.

The units 17 and 18 are angularly phased on the tube 15 so that thelower, or downstream, unit 18 pours its reagent into the tube 15 justahead of the upstream water sample being received into the tube so thatthe sample, in effect, washes all of the reagent along. To insure thatliquid in the center tube 15 will not spill back into the unit 18, anintroduction tube 53,fitted into the center tube 15, opens from the tubeopening 42 to the opposite side of the center tube 15. Thus, with thepocket 41 above the axis of the tube 15, liquid spills through theopening 42 and through the introduction tube 53 directly into the pathof the onflowing water sample at the bottom of the center tube. Furtherrotation of the center tube places the introduction tube opening abovethe then bottom of the center tube (see FIG. 3a) so that, in the eventthat there is some residual liquid in the tube, that liquid will notflow back into the pocket 41 to disturb the accuracy of the next reagentmeasurement.

It will be recalled that the unit 18 in the illustrated analyzer is ameasuring, mixing and holding unit intended to mix 0.] ml. of ammoniummolybdate with 5.0 ml. of water and to hold that mixture for 5 minutes.The mixing and holding portion of the unit 18 comprises a body 55 in theform of a disk having a liquid receiving core fitted tightly on thecenter tube and a spiraling passage 56 leading from the periphery of thebody 55 to an opening 57 in the tube 15. Preferably, the passage 56 ismilled into one face of the disk body 55 and is closed by the bodies 40,55 being sealed to one another. The liquid solution is introduced to theouter end of the spiraling passage 56 through a generally radial passage58 formed in the body 40 which connects a pair of openings 59 and 61 andis sealed by a plug 62 adjacent the opening 61. A wall 63 within thetube 15 provides a fluid-tight block to fluid flow down the tube so thatliquid introduced by the units 17 and 18 is forced into the opening 59and through the passage 58 to the opening 61 and the spiraling passage56 (see FIGS. 3b and 5).

In the illustrated analyzer, the synchronous motor 16 rotates the tube15, and thus the units 17-20, at the rate of one revolution per minute.Thus, the passage 56 is spiraled five times about the axis of the tube15 with the result that five revolutions, and five minutes, are requiredto have fluid flow along the passage 56 from the opening 61 to theopening 57 which leads back into the center tube 15 on the downstreamside of the blocking wall 63.

To avoid having the liquid in the passage 56 bridge that passage andpossibly develop a blocking bubble, the passage 56 is formed, with anincreasing cross section as the radius of the spiral increases (see FIG.4).

The measuring and mixing unit includes measuring structure virtuallyidentical to that found in the unit 18 and therefore it will beidentified with the same reference numerals havingthe distinguishingsuffix a added. Thus, the measuring portion of the unit 20 includes abody 40a defining a pocket 41a whose volume is adjusted by a member 45aand whose upper edge is defined by a spill wall edge 43a. The pocket isfilled by a lifting passage 44a, and the pocket pours that reagent,

upon continued rotation of the tube 15, into an opening 42a in the tubeand through an introduction tube 53a. The units 18 and 20 are angularlyphased on the tube 15 so that, in the illustrated analyzer 10, 0.1 ml.of oxalic acid from the container 23 is poured intothe center tubethrough the introduction tube 53a just as the 5.1 ml. of solution ispoured from the body 55 so that the further reagent is washed along.

The mixing portion of the unit 20 includes a body 65 in the form of adisk having a liquid receiving core fitted tightly onthe center tube 15,a pair of openings 66 and 67 angularly spaced about the axis of the tube15 which serve as inlet and outlet openings, and a tortuous serpentinepath 68 defined by spoke-like recesses connecting the openings 66, 67.The path 68 is preferably formed by milling the recesses into the faceof the body 65 with the passage being closed by the bodies 65 and 40abeing sealed to one another. A passage 69 is formed in the body 40aadjacent a wall 63a in the tube 15 (see FIG. 7) which leads to anddefines the opening 66. As will be apparent, solution poured through theopening 66 will, upon rotation of the unit 20, spill from one spoke ofthe recess into the next along the serpentine passage 68 so as tothoroughly mix the solution.

The unit 19, a measuring, mixing and holding unit, is identical to theunit 18 and will not therefore be described in greater detail. In theillustrated analyzer 10, the unit 19 functions to add 0.1 ml. of aminoacid solution from the container 24 to the previously mixed solutionalready traveling down the tube 15. Unit 19 is angularly phased withrespect to the unit 20 so that the reagent is poured into the tube 15from the unit 19 just as the solution flows down from the upstreamunit20. Following the 5-minute holding and mixing cycle developed by theunit 19, the solution is poured from that unit back into the tube 15,from which it flows through a collar 70 (see FIG. 10) into thecolorimeter 21. Appropriate filters and light sensors in the colorimeterrespond to the development of the test color, blue in this case, so asto indicate the presence or absence of silica in the water sample undertest.

It will be appreciated that the analyzer 10 is a continuously cyclingapparatus, and that a number of samples will be simultaneously in theprocess of passing through the various units 17-20. Once all of theunits are, in effect, full then successive checks will be made everyrevolution of the tube 15, i.e., every minute. Upon startup, it isdesirable to allow several samples to pass completely through theanalyzer so that proportioning of the reagents can become stabilized. Itwill be noted that, for example, the unit 20 will deposit about sixmeasured amounts of the reagent associated with that unit in the tube 15before the first water sample reaches that unit so that, until a fewsamples have passed through theentire analyzer, the possibility ofinaccurate proportioning in the solution exists.

The tanks 22-24 are preferably formed in two pieces, having spaciousbottom portions 71 to contain a longlasting quantity of reagent, andtops 72 which enclose the respective units as well as the tank bottomsso as to avoid contamination. Filler holes and plugs 73 permitconvenient replenishing of the reagent contents, and the openingsthrough which the center tube 15 passes are preferably closed by annularflap valves 74.

Those skilled in this art will appreciate that the analyzer 10 can bemanufactured quite economically, particularly when it is compared withthose analyzers requiring expensive pumps and valving. The analyzer 10also operates accurately and reliably while requiring virtually nomaintenance. The analyzer is quite temperature stable since there are nocritical flow rates which might be affected by a change in the viscosityof the liquids being handled.

It can also be seen that the components of the analyzer 10 are quiterugged and, indeed, there is virtually but a single moving part whichcan be quite solidly made. This rugged, simple construction has beenachieved despite the relatively sophisticated nature of the analysisbeing carried out.

It has already been pointed out that a wide variety of tests can be setup by arranging the components of the analyzer 10 so as to produce adesired sequence of measuring, mixing and holding virtually any numberof reagents with the sample under investigation.

I claim as my invention:

1. A liquid measuring and feeding'unit for automatic analyzerscomprising a body having a liquid receiving core at an axis about whichthe body rotates, said body defining a measuring pocket adjacent saidcore and having an open top open to the core, said pocket also having aspill wall side for defining the top of the pocket and thus the upperlevel of liquid in the pocket when the pocket is beneath said axis, saidbody also defining a lifting passage leading from the top of said pocketto a point well spaced from said axis, said passage including a bottomsurface generally facing said axis so that rotation of the body thereonwith the axis generally parallel to a supply of liquid will sequentiallycause the surface to dip into the liquid, raise a quantity of liquidfrom said supply and pour the raised liquid quantity into said pocket,and said passage being proportioned to raise and pour into said pocket avolume of liquid greater than that retained by said spill wall side.

2. The unit of claim 1 in which the edge of said spill wall adjacentsaid core is rounded and hydrophilic so that liquid spills smoothlythereover with minimum capillary effect, and said edge is curved aboutsaid axis to maintain a substantially fixed wall height through a rangeof body rotation about said axis.

3. The unit of claim 1 including, in combination, a member adjustablymounted in said body for movement into or out of said pocket so as toselectively vary the volume of the pocket.

4. The unit of claim 1 in which said passage has a cross sectionsufficiently large so as not to be bridged by liquid being conveyed tosaid pocket.

5. A liquid holding and mixing unit for automatic analyzers comprising abody having a liquid receiving core and an axis about which the bodyrotates, said body defining a spiraling passage leading from the bodyperiphery to an opening at said core, and said body also having a liquidintroduction opening for allowing liquid to flow into the peripheral endof said passage whereby the liquid will flow into said core after apredetermined number of body revolutions about said axis.

6. The combination of claim 5 in which said spiraling passage is formedwith an increasing cross section as the radius of the spiral decreasesso as to avoid having the liquid volume bridge the passage.

7. A liquid mixing unit for automatic analyzers comprising a body havinga liquid receiving core at an axis about which the body rotates, saidbody having a pair of openings angularly spaced about said axis forserving as inlet and outlet openings, and said body also having atortuous serpentine path connecting said pair of openings so that, uponrotation of said body, liquid introduced through one opening is mixingby spilling along said passage before exiting through the other openlng.

8. An analyzer comprising, in combination, a frame, a center tubemounted for rotation in said frame and being disposed at an angle withrespect to the horizontal so as to have a high end and a low end, acolorimeter in said frame having a liquid receiving passage beneath thelower end of said tube, a plurality of liquid containers in said framespaced beneath said tube, a plurality of liquid measuring and feedingunits mounted on said tube for rotation into respective ones of saidcontainers upon rotation of the tube, and means in said frame forrotating said tube so that said units lift liquid from said containers,spill back all but a measured volume and pour that volume into saidtube, said tube having an opening above said colorimeter so that thetotal of said measured liquid volumes flows into the colorimeter.

9. The combination of claim 8 including an introduction tube fitted intosaid center tube and opening from one of said units to the opposite sideof the center tube on which the unit is mounted so that liquid in thecenter tube will not spill back into said one unit.

10. The combination of claim 8 including a mixing unit mounted on saidcenter tube at a lower tube portion than where a pair of said measuringand feeding units are mounted, said mixing unit being open to the tubefor receiving liquid and having a path for spilling the liquid through atortuous path upon rotation of the center tube before allowing theliquid to flow to said colorimeter.

11. The combination of claim 8 including a mixing and holding unitmounted on said center tube at a lower tube portion than where a pair ofsaid measuring and feeding units are mounted, said mixing and holdingunit being open to the tube for receiving liquid and having a path forspilling the liquid through a spiraling path upon rotation of the centertube through a predetermined number of revolutions before allowing theliquid to flow to said colorimeter.

1. A liquid measuring and feeding unit for automatic analyzerscomprising a body having a liquid receiving core at an axis about whichthe body rotates, said body defining a measuring pocket adjacent saidcore and having an open top open to the core, said pocket also having aspill wall side for defining the top of the pocket and thus the upperlevel of liquid in the pocket when the pocket is beneath said axis, saidbody also defining a lifting passage leading from the top of said pocketto a point well spaced from said axis, said passage including a bottomsurface generally facing said axis so that rotation of the body thereonwith the axis generally parallel to a supply of liquid will sequentiallycause the surface to dip into the liquid, raise a quantity of liquidfrom said supply and pour the raised liquid quantity into said pocket,and said passage being proportioned to raise and pour into said pocket avolume of liquid greater than that retained by said spill wall side. 2.The unit of claim 1 in which the edge of said spill wall adjacent saidcore is rounded and hydrophilic so that liquid spills smoothly thereoverwith minimum capillary effect, and said edge is curved about said axisto maintain a substantially fixed wall height through a range of bodyrotation about said axis.
 3. The unit of claim 1 including, incombination, a member adjustably mounted in said body for movement intoor out of said pocket so as to selectively vary the volume of thepocket.
 4. The unit of claim 1 in which said passage has a cross sectionsufficiently large So as not to be bridged by liquid being conveyed tosaid pocket.
 5. A liquid holding and mixing unit for automatic analyzerscomprising a body having a liquid receiving core and an axis about whichthe body rotates, said body defining a spiraling passage leading fromthe body periphery to an opening at said core, and said body also havinga liquid introduction opening for allowing liquid to flow into theperipheral end of said passage whereby the liquid will flow into saidcore after a predetermined number of body revolutions about said axis.6. The combination of claim 5 in which said spiraling passage is formedwith an increasing cross section as the radius of the spiral decreasesso as to avoid having the liquid volume bridge the passage.
 7. A liquidmixing unit for automatic analyzers comprising a body having a liquidreceiving core at an axis about which the body rotates, said body havinga pair of openings angularly spaced about said axis for serving as inletand outlet openings, and said body also having a tortuous serpentinepath connecting said pair of openings so that, upon rotation of saidbody, liquid introduced through one opening is mixing by spilling alongsaid passage before exiting through the other opening.
 8. An analyzercomprising, in combination, a frame, a center tube mounted for rotationin said frame and being disposed at an angle with respect to thehorizontal so as to have a high end and a low end, a colorimeter in saidframe having a liquid receiving passage beneath the lower end of saidtube, a plurality of liquid containers in said frame spaced beneath saidtube, a plurality of liquid measuring and feeding units mounted on saidtube for rotation into respective ones of said containers upon rotationof the tube, and means in said frame for rotating said tube so that saidunits lift liquid from said containers, spill back all but a measuredvolume and pour that volume into said tube, said tube having an openingabove said colorimeter so that the total of said measured liquid volumesflows into the colorimeter.
 9. The combination of claim 8 including anintroduction tube fitted into said center tube and opening from one ofsaid units to the opposite side of the center tube on which the unit ismounted so that liquid in the center tube will not spill back into saidone unit.
 10. The combination of claim 8 including a mixing unit mountedon said center tube at a lower tube portion than where a pair of saidmeasuring and feeding units are mounted, said mixing unit being open tothe tube for receiving liquid and having a path for spilling the liquidthrough a tortuous path upon rotation of the center tube before allowingthe liquid to flow to said colorimeter.
 11. The combination of claim 8including a mixing and holding unit mounted on said center tube at alower tube portion than where a pair of said measuring and feeding unitsare mounted, said mixing and holding unit being open to the tube forreceiving liquid and having a path for spilling the liquid through aspiraling path upon rotation of the center tube through a predeterminednumber of revolutions before allowing the liquid to flow to saidcolorimeter.